Long Term Evolution/Evolved Packet Core (LTE/EPC) is standardized in 3GPP Release 8. The system includes 3GPP as well as non-3GPP system access. In a core network the Proxy Mobile IP (PMIP) protocol can be used as mobility protocol. When PMIP is used, basic IP connectivity is provided in the core network between the Packet Data Network Gateway (PGW) and the User Equipment (UE), e.g. a mobile phone. Compared to GPRS Tunneling Protocol (GTP) mobility protocol, the PMIP protocol provides simpler and limited functionality. In particular the bearer handling is simplified.
The system architecture of an existing solution is shown in FIG. 1, where a user equipment 3 is connected to a Evolved Universal Terrestrial Radio Access Network (EUTRAN). The system has a Mobility Management Entity (MME) providing control-plane functionality and giving orders to the Signaling Gateway (SGW). A Home Subscriber Server (HSS) is connected to the MME and describes the many database functions in the network. The Packet Data Network Gateway (PGW) 13 provides connectivity between the user equipment 3 and external networks. The Policy and Charging Rules Function (PCRF) 6 is connected between the PGW 13 and an operator's IP services 8, such as IMS, PSS etc. and takes care of policy and charging issues between the user equipment 3 and the operator. In the existing solution the core network (CN) interfaces S5/S8 can be PMIP or GTP based. The S2 interfaces are PMIP based. The PMIP based interfaces are marked with dashed lines in FIG. 1. The serving gateway (SGW) 12 or the non-3GPP access system 7 acts as an (Mobile Access Gateway) MAG, while the PGW 13 act as the local mobile anchor (LMA) using PMIP terminology.
When the user equipment first attaches the system (i.e. connects to the cellular network) it includes parameters to indicate relevant connection information, e.g. the Access Point Name (APN). The APN indicates to which external network (public data network, PDN) the user equipment wants to connect and it can be used in the network to select the proper PGW to handle the user equipment. The PGW can provide connectivity to several external networks and the APN is used also inside the PGW to connect to the correct external network.
When the user equipment has several connections activated and is detached, all its public data network connections need to be deleted or closed. Currently there exist several methods to close such network connections. Public data network connections can be closed individually for each user equipment or as a bulk closing for an entire network node. As of today, the MAG needs to send one Proxy Binding Update (PBU) message per public data network connection per user equipment, which implies several messages. When the user equipment has multiple public data network connections to different or to the same APN, a number of PBU/PBA (Proxy Binding Acknowledgement) must be sent from the MAG to the LMA. Thus, signaling bandwidth is wasted.
When public data network connections are removed on a PMIP interface there exist different procedures. One procedure is that the LMA may send a Binding Revocation Indication (BRI) message to the MAG, hosting a specific proxy mobile IPv6 session. The BRI message has the appropriate value in the revocation trigger field to indicate that the mobile node binding has been terminated and the MAG can clean up the applicable resources. In a second possible procedure the LMA sends a BRI message to indicate that all bindings which are hosted by the peer MAG and registered with the LMA are being revoked. For this second procedure, the BRI can only be sent in the direction from the LMA to the MAG. In a third possible procedure, the MAG sends a BRI message with the G bit set to indicate that all mobility sessions which are registered at the LMA and attached to the MAG are being revoked. For the third procedure which is in the direction from the MAG to the LMA, the BRI message with G bit set cannot be used to revoke all sessions related to a user equipment. It only can be used to revoke all sessions related to the MAG. A drawback with the BRI message for second and third procedure is that when the G bit is set by the sending mobility node, LMA or MAG, it requests the termination of all Per-Peer mobility Bindings or Multiple Bindings which share a common identifier that are served by the sending and receiving mobility entities. And in another procedure the MAG sends a PBU for one public data network connection at the time with the “TimeToLive” value=zero. Then the connection is removed in the LMA. A drawback for this last procedure is that the PBU (with lifetime=0) can only remove one session.